Method for strengthening cellulosic substrates

ABSTRACT

This invention relates to a method for strengthening a cellulosic substrate by treating the substrate with a formaldehyde-free curable aqueous composition and curing the composition. The cellulosic substrates include, for example, paper oil- and air-filter stock, rayon nonwoven wipes, cellulosic laminating stock, cotton woven fabrics, and wood flakes suitable to be consolidated into flakeboard.

FIELD OF THE INVENTION

This invention relates to a method for strengthening a cellulosicsubstrate by treating the substrate with a formaldehyde-free curableaqueous composition and curing the composition. The curable compositioncontains (a) a polyacid containing at least two carboxylic acid groups,anhydride groups, or the salts thereof; (b) optionally, an activehydrogen compound containing at least two active hydrogen groupsselected from the group consisting of hydroxyl, primary amino, secondaryamino, and mixtures thereof; and (c) a phosphorous-containingaccelerator, wherein the ratio of the number of equivalents of saidcarboxylic acid groups, anhydride groups, or salts thereof to the numberof equivalents of said active hydrogen groups is from about 1/0.01 toabout 1/3, and wherein the carboxyl groups, anhydride groups, or saltsthereof are neutralized to an extent of less than about 35% with a fixedbase. The composition is applied to a substrate composed predominantlyof cellulosic components. Such substrates include, for example, paperoil- and air-filter stock, rayon nonwoven wipes, polyester/cotton wovenfabrics, cellulosic laminating stock, nonwoven cellulosic felts, andwood fibers and flakes consolidated into or suitable to be consolidatedinto fiberboard, hardboard, particleboard, and oriented strand board.

BACKGROUND OF THE INVENTION

Substrates composed predominantly of cellulosic materials are frequentlyadvantageously strengthened by treatment with a polymeric composition.The treatment with a polymeric composition may also provide reducedsensitivity to moisture vapor or water or solvents in addition toreinforcement of the substrate. Furthermore, the polymeric compositionshould not substantially detract from essential substratecharacteristics, as might be the case, for example, if the curedcomposition were too rigid or brittle or became sticky under processingconditions. Additionally, the polymeric composition should wet out andpenetrate preformed cellulosic webs and mats.

There is a need for a method for strengthening cellulosic substrates bytreating with a curable aqueous composition which is free fromformaldehyde, because of existing and proposed legislation directed tothe lowering or elimination of formaldehyde.

DESCRIPTION OF THE PRIOR ART

U.S. Pat. No. 5,042,986 discloses an aqueous treating solution forcellulosic textiles, the treating solution containing a cyclic aliphatichydrocarbon of 4 to 6 carbon atoms having 4 or more carboxyl groupswherein at least two adjacent carboxyl groups are in the transconfiguration relative to each other. The treating solution includes asuitable curing agent which is the alkali metal dihydrogen phosphate orthe alkali metal salt of phosphorous, hypophosphorous, andpolyphosphoric acid. The treating process is disclosed to beadvantageously used with textiles containing 30-100% cellulosicmaterials.

U.S. Pat. Nos. 4,820,307; 4,936,865; and 4,975,209 disclose catalystsfor the rapid formaldehyde-free esterification and crosslinking offibrous cellulose in textile form by polycarboxylic acids includingsaturated, unsaturated, and aromatic acids as well asalpha-hydroxyacids. The catalysts disclosed are acidic or weakly basicsalts selected from the alkali metal dihydrogen phosphates and alkalimetal salts of phosphorous, hypophosphorous, and polyphosphoric acids.

U.S. Pat. No. 4,795,533 discloses a solid electrolyte membrane whichcontains a three component blend prepared by admixing an organicpolymer, such as polyvinyl alcohol, with an inorganic compound and apolyorganic acid, such as polyacrylic acid. The inorganic compound isdisclosed to be selected from a group consisting of phosphoric acid,sulphuric acid, heteropoly acids, or salts of heteropoly acids. Examplesof phosphoric acids which may be employed include hypophosphorous acid,metaphosphoric acid, orthophosphoric acid, pyrophosphoric acid, andpolyphosphoric acid.

U.S. Pat. No. 4.076,917 discloses β-hydroxyalkylamides and certainpolymers thereof as curing agents for polymers containing one or morecarboxy or anhydride functions. The β-hydroxyamides are disclosed to beeffective in solution, aqueous emulsion, and powder coating form.

None of the references disclose treating a cellulosic substrate with theformaldehyde-free curable aqueous composition of this invention. Thecomposition contains (a) a polyacid containing at least two carboxylicacid groups, anhydride groups, or the salts thereof; (b) optionally, anactive hydrogen compound containing at least two active hydrogen groupsselected from the group consisting of hydroxyl, primary amino, secondaryamino, and mixtures thereof; and (c) a phosphorous-containingaccelerator, wherein the ratio of the number of equivalents of saidcarboxylic acid groups, anhydride groups, or salts thereof to the numberof equivalents of said active hydrogen groups is from about 1/0.01 toabout 1/3, and wherein the carboxyl groups, anhydride groups, or saltsthereof are neutralized to an extent of less than about 35% with a fixedbase.

STATEMENTS OF THE INVENTION

According to a first aspect of this invention there is provided a methodfor strengthening a cellulosic substrate by treating the substrate witha formaldehyde-free curable aqueous composition and curing thecomposition.

According to a second aspect of this invention there is provided amethod for increasing the solvent- and water-wet strength and drystrength of a cellulosic nonwoven wipe by treating the substrate with aformaldehyde-free curable aqueous composition and curing thecomposition.

According to a third aspect of this invention there is provided a methodfor increasing the solvent- and water-wet strength and dry strength ofpaper oil- and air-filter stock by treating the substrate with aformaldehyde-free curable aqueous composition and curing thecomposition.

According to a fourth aspect of this invention there is provided amethod for increasing the delamination resistance of cellulosic foils orlaminates by treating the cellulosic laminating stock with aformaldehyde-free curable aqueous composition and curing thecomposition. And a method for forming multi-ply laminates which arebonded together and are capable of forming moldable, B-stageablelaminates.

According to a fifth aspect of this invention there is provided a methodfor improving the permanent-press performance of cellulosic wovenfabrics by treating the substrate with a formaldehyde-free curableaqueous composition and curing the composition.

According to a sixth aspect of this invention there is provided a methodfor improving the water resistance of a consolidated wood product bytreating the wood components such as, for example, fibers and flakes,prior to consolidation, with a formaldehyde-free curable aqueouscomposition and curing the composition.

DETAILED DESCRIPTION OF THE INVENTION

A method for strengthening a cellulosic substrate by treating thesubstrate with a formaldehyde-free curable aqueous composition andcuring the composition is provided. The curable composition contains (a)a polyacid containing at least two carboxylic acid groups, anhydridegroups, or the salts thereof; (b) optionally, an active hydrogencompound containing at least two active hydrogen groups selected fromthe group consisting of hydroxyl, primary amino, secondary amino, andmixtures thereof; and (c) a phosphorous-containing accelerator, whereinthe ratio of the number of equivalents of said carboxylic acid groups,anhydride groups, or salts thereof to the number of equivalents of saidactive hydrogen groups is from about 1/0.01 to about 1/3, and whereinthe carboxyl groups, anhydride groups, or salts thereof are neutralizedto an extent of less than about 35% with a fixed base. The compositionis applied to a substrate composed predominantly of cellulosiccomponents. Such substrates include, for example, paper oil- andair-filter stock, rayon nonwoven wipes, polyester/cotton woven fabrics,cellulosic laminating stock, and wood fibers and flakes consolidatedinto or suitable to be consolidated into fiberboard, hardboard, particleboard, and oriented strand board. By "strengthening a cellulosicsubstrate" herein is meant that at least one of the mechanicalproperties such as, for example, dry tensile strength and wet tensilestrength of the substrate treated and cured according to the method ofthis invention is increased over the same property of the untreatedsubstrate.

The formaldehyde-free curable aqueous composition of this invention is asubstantially thermoplastic, or substantially uncrosslinked, compositionwhen it is applied to the substrate, although low levels of deliberateor adventitious crosslinking may be present. On heating the binder, thebinder is dried and curing is effected by heating, either sequentiallyor concurrently. By curing is meant herein that a chemical and/orphysical change has occured, for example, covalent chemical reaction,ionic interaction or clustering, improved adhesion to the substrate,phase transformation or inversion, hydrogen bonding, and the like.

This invention is directed to a formaldehyde-free curable aqueouscomposition. By "formaldehyde-free composition" herein is meant that thecomposition is substantially free from formaldehyde, nor does itliberate substantial formaldehyde as a result of drying and/or curing.In order to minimize the formaldehyde content of the waterbornecomposition it is preferred, when preparing a polymer-containingformaldehyde-free curable aqueous composition, to use polymerizationadjuncts such as, for example, initiators, reducing agents, chaintransfer agents, biocides, surfactants, and the like, which arethemselves free from formaldehyde, do not generate formaldehyde duringthe polymerization process, and do not generate or emit formaldehydeduring the treatment of a substrate composed predominantly of cellulosiccomponents. By "substantially free from formaldehyde" herein is meantthat when low levels of formaldehyde are acceptable in the waterbornecomposition or when compelling reasons exist for using adjuncts whichgenerate or emit low levels of formaldehyde, substantiallyformaldehyde-free waterborne compositions may be used.

The formaldehyde-free curable aqueous composition contains a polyacid.The polyacid must be sufficiently nonvolatile that it will substantiallyremain in the treated substrate during heating and curing operations.The polyacid may be a compound with a molecular weight less than about1,000 bearing at least two carboxylic acid groups, anhydride groups, orsalts thereof such as, for example, citric acid, butane tricarboxylicacid, and cyclobutane tetracarboxylic acid or it may be a polymericpolyacid with a molecular weight greater than about 1,000 such as, forexample, a polyester containing at least two carboxylic acid groups andan addition polymer or oligomer containing at least two copolymerizedcarboxylic acid-functional monomers. The polymeric polyacid ispreferably an addition polymer formed from at least one ethylenicallyunsaturated monomer. The addition polymer may be in the form of asolution of the addition polymer in an aqueous medium such as, forexample, an alkali-soluble resin which has been solubilized in a basicaqueous medium; in the form of an aqueous dispersion such as, forexample, an emulsion-polymerized dispersion; or in the form of anaqueous suspension. "Aqueous" herein includes water and mixturescomposed substantially of water and water-miscible solvents.

The polymeric polyacid addition polymer must contain at least twocarboxylic acid groups, anhydride groups, or salts thereof.Ethylenically unsaturated carboxylic acids such as, for example,methacrylic acid, acrylic acid, crotonic acid, fumaric acid, maleicacid, 2-methyl maleic acid, itaconic acid, 2-methyl itaconic acid,α,β-methylene glutaric acid, monoalkyl maleates, and monoalkylfumarates; ethylenically unsaturated anhydrides such as, for example,maleic anhydride, itaconic anhydride, acrylic anhydride, and methacrylicanhydride; and salts thereof, at a level of from about 1% to 100%, byweight, based on the weight of the addition polymer, may be used.Additional ethylenically unsaturated monomer may include acrylic estermonomers including methyl acrylate, ethyl acrylate, butyl acrylate,2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, butylmethacrylate, isodecyl methacrylate, hydroxyethyl acrylate, hydroxyethylmethacrylate, and hydroxypropyl methacrylate; acrylamide or substitutedacrylamides; styrene or substituted styrenes; butadiene; vinyl acetateor other vinyl esters; acrylonitrile or methacrylonitrile; and the like.

The polymeric polyacid addition polymer containing at least twocarboxylic acid groups, anhydride groups, or salts thereof may have amolecular weight from about 300 to about 10,000,000. Preferred is amolecular weight from about 1,000 to about 250,000. When the polymericpolyacid addition polymer is an alkali-soluble resin having a carboxylicacid, anhydride, or salt thereof, content of from about 5% to about 30%,by weight based on the total weight of the addition polymer, a molecularweight from about 5,000 to about 100,000 is preferred, higher molecularweight alkali-soluble resins leading to curable compositions which mayexhibit undesirably high application viscosity unless diluted to lowapplication solids.

When the polymeric polyacid addition polymer is in the form of anaqueous dispersion or an aqueous suspension a glass transitiontemperature between about 60 C., and about -50 C. is preferred. Glasstransition temperatures (Tgs) herein are those calculated as a weightedaverage of the homopolymer Tg values, that is, for calculating the Tg ofa copolymer of monomers M1 and M2,

    Tg(calc.)=w(M1)×Tg(M1)+w(M2)×Tg(M2),

wherein

Tg(calc.) is the glass transition temperature calculated for thecopolymer

w(M1) is the weight fraction of monomer M1 in the copolymer

w(M2) is the weight fraction of monomer M2 in the copolymer

Tg(M1) is the glass transition temperature of the homopolymer of M1

Tg(M2) is the glass transition temperature of the homopolymer of M2

The glass transition temperature of homopolymers may be found, forexample, in "Polymer Handbook", edited by J. Brandrup and E. H.Immergut, Interscience Publishers.

And, when the polymeric polyacid addition polymer is in the form of anaqueous dispersion or an aqueous suspension and low levels ofprecrosslinking or gel content are desired, multi-ethylenicallyunsaturated monomers such as, for example, allyl methacrylate, diallylphthalate, 1,4-butylene glycol dimethacrylate, 1,6-hexanedioldiacrylate,and the like, may be used at a level of from about 0.01% to about 5%, byweight based on the weight of the addition polymer.

When the polymeric polyacid addition polymer is in the form of anaqueous dispersion the diameter of the addition polymer particles may befrom about 45 nanometers to about 1000 nanometers, as measured using aBrookhaven Bl-90 Particle Sizer, which employs a light scatteringtechnique. However, polymodal particle size distributions such as thosedisclosed in U.S. Pat. Nos. 4,384,056 and 4,539,361, hereby incorporatedherein by reference, may be employed.

When the polymeric polyacid addition polymer is in the form of anaqueous dispersion the addition polymer particles may be made up of twoor more mutually incompatible copolymers. These mutually incompatiblecopolymers may be present in various morphological configurations suchas, for example, core/shell particles, core/shell particles with shellphases incompletely encapsulating the core, core/shell particles with amultiplicity of cores, interpenetrating network particles, and the like.

The polymeric polyacid addition polymer may be prepared by solutionpolymerization, emulsion polymerization, or suspension polymerizationtechniques for polymerizing ethylenically-unsaturated monomers which arewell known in the art. When it is desired to prepare the polymericpolyacid addition polymer by emulsion polymerization, anionic ornonionic surfactants, or mixtures thereof, may be used. Thepolymerization may be carried out by various means such as, for example,with all of the monomer in the reaction kettle at the beginning of thepolymerization reaction, with a portion of the monomer in emulsifiedform present in the reaction kettle at the beginning of thepolymerization reaction, and with a small particle size emulsion polymerseed present in the reaction kettle at the beginning of thepolymerization reaction.

The polymerization reaction to form the polymeric polyacid additionpolymer may be initiated by various methods known in the art such as,for example, by the thermal decomposition of an initiator and by anoxidation-reduction reaction ("redox reaction") to generate freeradicals to effect the polymerization. In another embodiment theaddition polymer may be formed in the presence of phosphorous-containingchain transfer agents such as, for example, hypophosphorous acid and itssalts, as is disclosed in U.S. Pat. No. 5,077,361, hereby incorporatedherein by reference, so as to incorporate the phosphorous-containingaccelerator and the polyacid component in the same molecule.

Chain transfer agents such as mercaptans, polymercaptans, and halogencompounds may be admixed with the polymerization mixture in order tomoderate the molecular weight of the acrylic emulsion copolymer.Generally, from 0% to about 1% by weight, based on the weight of thepolymeric binder, of C₄ -C₂₀ alkyl mercaptans, mercaptopropionic acid,or esters of mercaptopropionic acid, may be used.

The carboxyl groups of the polyacid component of the formaldehyde-freecurable aqueous composition are neutralized with fixed base to an extentof less than about 35%, calculated on an equivalents basis. Contactingthe polyacid component, defined as neutralization herein, before,during, or after the formation of the curable aqueous composition, thepolyacid containing two carboxylic acid groups, anhydride groups, or thesalts thereof, with a fixed base is required prior to treating acellulosic substrate. Neutralization of less than about 35% of thecarboxylic acid groups, calculated on an equivalents basis, with a fixedbase is required. Neutralization of less than about 20% of thecarboxylic acid groups, calculated on an equivalents basis, with a fixedbase is preferred. Neutralization of less than about 5% of thecarboxylic acid groups, calculated on an equivalents basis, with a fixedbase is more preferred. When the half ester of a dicarboxylic acid orthe anhydride of a dicarboxylic acid is used, the equivalents of acidare calculated to be equal to those of the corresponding dicarboxylicacid.

"Fixed base", or "permanent base", as used herein, is defined as amonovalent base which is substantially non-volatile under the conditionsof the treatment such as, for example, sodium hydroxide, potassiumhydroxide, sodium carbonate, or t-butylammonium hydroxide. Excluded fromthe definition of fixed base is any active hydrogen compound containingat least two active hydrogen groups selected from the group consistingof hydroxyl, primary amino, secondary amino, and mixtures thereof. Thefixed base must be sufficiently nonvolatile that it will substantiallyremain in the composition during heating and curing operations. Volatilebases such as, for example, ammonia or volatile lower alkyl monoamines,do not function as the fixed base of this invention, but may be used inaddition to the fixed base; they do not contribute to the requireddegree of neutralization by a fixed base. Fixed multivalent bases suchas, for example, calcium carbonate may tend to destabilize an aqueousdispersion, if the addition polymer is used in the form of an aqueousdispersion, but may be used in minor amount.

The formaldehyde-free curable aqueous composition may contain an activehydrogen compound containing at least two active hydrogen groupsselected from the group consisting of hydroxyl, primary amino, secondaryamino, and mixtures thereof. The active hydrogen compound must besufficiently nonvolatile that it will substantially remain available forreaction with the polyacid in the composition during heating and curingoperations. The active hydrogen compound may be a compound with amolecular weight less than about 1000 bearing at least two activehydrogen groups groups such as, for example, ethylene glycol, glycerol,pentaerythritol, trimethylol propane, sorbitol, sucrose, glucose,resorcinol, catechol, pyrogallol, glycollated ureas, 1,4-cyclohexanediol, diethanolamine, triethanolamine, and certain reactive polyols suchas, for example, β-hydroxyalkylamides such as, for example,bis-[N,N-di(β-hydroxyethyl)]adipamide, as may be prepared according tothe teachings of U.S. Pat. No. 4,076,917, hereby incorporated herein byreference, or it may be an addition polymer with a molecular weightgreater than about 1000 containing at least two active hydrogen groupsgroups such as, for example, polyvinyl alcohol, partially hydrolyzedpolyvinyl acetate, and homopolymers or copolymers of hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate, dimethylaminoethylmethacrylate. dimethylaminopropyl methacrylamide, and the like.

The ratio of the number of equivalents of carboxy, anhydride, or saltsthereof of the polyacid to the number of equivalents of active hydrogengroup in the active hydrogen compound is from about 1/0.01 to about 1/3.An excess of equivalents of carboxy, anhydride, or salts thereof of thepolyacid to the equivalents of hydroxyl in the polyol is preferred. Themore preferred ratio of the number of equivalents of carboxy, anhydride,or salts thereof in the polyacid to the number of equivalents of activehydrogen group in the active hydrogen compound is from about 1/0.2 toabout 1/1. The most preferred ratio of the number of equivalents ofcarboxy, anhydride, or salts thereof in the polyacid to the number ofequivalents of hydroxyl in the polyol is from about 1/0.2 to about1/0.8.

The formaldehyde-free curable aqueous composition also contains aphosphorous-containing accelerator which may be a compound with amolecular weight less than about 1000 such as, for example, an alkalimetal hypophosphite salt, an alkali metal phosphite, an alkali metalpolyphosphate, an alkali metal dihydrogen phosphate, a polyphosphoricacid, hypophosphorous acid, phosphorous acid, and an alkyl phosphinicacid or it may be an oligomer or polymer bearing phosphorous-containinggroups such as, for example, addition polymers of acrylic and/or maleicacids formed in the presence of sodium hypophosphite, addition polymersprepared from ethylenically unsaturated monomers in the presence ofphosphorous salt chain transfer agents or terminators, and additionpolymers containing acid-functional monomer residues such as, forexample, copolymerized phosphoethyl methacrylate, and like phosphonicacid esters, and copolymerized vinyl sulfonic acid monomers, and theirsalts. The phosphorous-containing accelerator may be used at a level offrom about 0.1% to about 40%, by weight based on the combined weight ofthe polyacid and the active hydrogen compound. Preferred is a level ofphosphorous-containing accelerator of from about 0.2% to about 10%, byweight based on the combined weight of the polyacid solids and theactive hydrogen compound.

The formaldehyde-free curable aqueous composition may contain, inaddition, conventional treatment components such as, for example,emulsifiers, pigments, fillers, anti-migration aids, curing agents,coalescents, wetting agents, biocides, plasticizers, organosilanes,anti-foaming agents, colorants, waxes, and anti-oxidants.

The formaldehyde-free curable aqueous composition may be prepared byadmixing the polyacid, the active hydrogen compound, and thephosphorous-containing accelerator using conventional mixing techniques.In another embodiment a carboxyl- or anhydride-containing additionpolymer and an active hydrogen compound may be present in the sameaddition polymer. In another embodiment the salts of the carboxyl-groupare salts of functional alkanolamines such as, for example,diethanolamine, triethanolamine, dipropanolamine, anddiisopropanolamine. In another embodiment the active hydrogen groups andthe phosphorous-containing accelerator may be present in the sameaddition polymer, which addition polymer may be mixed with a polyacid.In another embodiment the carboxyl- or anhydride-groups, the activehydrogen groups, and the phosphorous-containing accelerator may bepresent in the same addition polymer. In some embodiments, the hydroxylgroups of cellulose may react with the polyacid. Other embodiments willbe apparent to one skilled in the art.

As disclosed herein-above, the carboxyl groups of the polyacid must beneutralized to to an extent of less than about 35% with a fixed basebefore, during, or after forming the curable aqueous composition.Neutralization may be partially or wholly effected during the formationof the polyacid.

The formaldehyde-free curable aqueous composition may be applied to anonwoven by conventional techniques such as, for example, air-assistedspraying, airless spraying, padding, saturating, roll coating, curtaincoating, beater deposition, coagulation, or the like.

The waterborne formaldehyde-free composition, after it is applied to anonwoven, is heated to effect drying and curing. The duration andtemperature of heating will affect the rate of drying, processabilityand handleability, and property development of the treated substrate.Heat treatment at about 120 C. to about 400 C. for a period of timebetween about 3 seconds to about 15 minutes may be carried out;treatment at about 150 C. to about 200 C. is preferred. Heating may beeffected in conjunction with the application of pressure. The drying andcuring functions may be effected in two or more distinct steps, ifdesired. For example, the composition may be first heated at atemperature and for a time sufficient to substantially dry but not tosubstantially cure the composition and then heated for a second time ata higher temperature and/or for a longer period of time to effectcuring. Such a procedure, referred to as "B-staging", may be used toprovide binder-treated nonwoven, for example, in roll form, which may ata later stage be cured, with or without forming or molding into aparticular configuration, concurrent with the curing process.

The treated cellulosic substrates may be used for applications such as,for example, laminates, industrial wipes, durable-press clothing, andoil and air filters, and consolidated wood products.

Nonwoven cellulosic wipes are beneficially strengthened under dry,water-wet and solvent-wet conditions which may be met in their use.

Oil-and air filter stock is beneficially strengthened to give thecomposite integrity at high temperatures and, in the case of oil filterapplications, when saturated with hot oil. B-stageability is abeneficial property in order to provide for drying of the curablecomposition and subsequent fluting and curing to form a stablestructure.

"Laminating stock" as used herein denotes cellulosic flat stock whichmay be used in pressure laminating processes or in decorative foilapplications. Pressure laminating processes build up a laminate from atleast two layers or plies of treated stock; the dried but substantiallyuncured treatment participates in bonding the files of the formedlaminate. Decorative laminate foils are treated, and usually cured,cellulosic stock which may be subsequently adhered to a substrate suchas, for example, particle board, to form a laminate.

PREFERABLE FEATURES

In a first aspect of this invention there is provided a method forstrengthening a cellulosic substrate by treating the substrate with aformaldehyde-free curable aqueous composition and curing thecomposition. Preferably, the curable composition contains (a) a polyacidcontaining at least two carboxylic acid groups, anhydride groups, or thesalts thereof; (b) optionally, an active hydrogen compound containing atleast two active hydrogen groups selected from the group consisting ofhydroxyl, primary amino, secondary amino, and mixtures thereof; and (c)a phosphorous-containing accelerator, wherein the ratio of the number ofequivalents of said carboxylic acid groups, anhydride groups, or saltsthereof to the number of equivalents of said active hydrogen groups isfrom about 1/0.01 to about 1/3, and wherein the carboxyl groups,anhydride groups, or salts thereof are neutralized to an extent of lessthan about 35% with a fixed base.

According to a second aspect of this invention there is provided amethod for increasing the solvent- and water-wet strength and drystrength of a cellulosic nonwoven wipe by treating the substrate with aformaldehyde-free curable aqueous composition and curing thecomposition. Preferably, the curable composition contains (a) acopolymer prepared by emulsion polymerization of at least twoethylenically-unsaturated monomers and containing at least twocarboxylic acid groups, anhydride groups, or the salts thereof; whereinsaid copolymer has a Tg between about 60 C. and about -50 C.; (b)optionally, an active hydrogen compound containing at least two activehydrogen groups selected from the group consisting of hydroxyl, primaryamino, secondary amino, and mixtures thereof; and (c) aphosphorous-containing accelerator, wherein the ratio of the number ofequivalents of said carboxylic acid groups, anhydride groups, or saltsthereof to the number of equivalents of said active hydrogen groups isfrom about 1/0.01 to about 1/3, and wherein the carboxyl groups,anhydride groups, or salts thereof are neutralized to an extent of lessthan about 35% with a fixed base.

According to a third aspect of this invention there is provided a methodfor increasing the solvent- and water-wet strength and dry strength ofpaper oil- and air-filter stock by treating the substrate with aformaldehyde-free curable aqueous composition and curing thecomposition. Preferably, the curable composition contains (a) a polyacidformed from at least one ethylenically-unsaturated monomer bearing acarboxylic acid group, anhydride group, or a salt thereof; (b)optionally, an active hydrogen compound containing at least two activehydrogen groups selected from the group consisting of hydroxyl, primaryamino, secondary amino, and mixtures thereof; and (c) aphosphorous-containing accelerator, wherein the ratio of the number ofequivalents of said carboxylic acid groups, anhydride groups, or saltsthereof to the number of equivalents of said active hydrogen groups isfrom about 1/0.01 to about 1/3, and wherein the carboxyl groups,anhydride groups, or salts thereof are neutralized to an extent of lessthan about 35% with a fixed base.

According to a fourth aspect of this invention there is provided amethod for increasing the dry strength and delamination resistance of acellulosic laminate stock by treating the substrate with aformaldehyde-free curable aqueous composition and curing the compositionand a method for forming laminated, moldable composites from the paperdecorative laminate stock. Preferably, the curable composition contains(a) a polyacid formed from at least one ethylenically-unsaturatedmonomer bearing a carboxylic acid group, anhydride group or a saltthereof and/or a copolymer prepared by emulsion polymerization of atleast two ethylenically-unsaturated monomers and containing at least twocarboxylic acid groups, anhydride groups, or the salts thereof; whereinsaid copolymer has a Tg between about 60 C. and about -50 C.; (b)optionally, an active hydrogen compound containing at least two activehydrogen groups selected from the group consisting of hydroxyl, primaryamino, secondary amino, and mixtures thereof; and (c) aphosphorous-containing accelerator, wherein the ratio of the number ofequivalents of said carboxylic acid groups, anhydride groups, or saltsthereof to the number of equivalents of said active hydrogen groups isfrom about 1/0.01 to about 1/3, and wherein the carboxyl groups,anhydride groups, or salts thereof are neutralized to an extent of lessthan about 35% with a fixed base.

According to a fifth aspect of this invention there is provided a methodfor improving the permanent-press performance of cellulosic wovenfabrics by treating the substrate with a formaldehyde-free curableaqueous composition and curing the composition. Preferably, the curablecomposition contains (a) a polyacid containing at least two carboxylicacid groups, anhydride groups, or the salts thereof, the polyacidfurther comprising a phosphinate group; (b) optionally, an activehydrogen compound containing at least two active hydrogen groupsselected from the group consisting of hydroxyl, primary amino, secondaryamino, and mixtures thereof; and (c) optionally, aphosphorous-containing accelerator, wherein the ratio of the number ofequivalents of said carboxylic acid groups, anhydride groups, or saltsthereof to the number of equivalents of said active hydrogen groupsgroups is from about 1/0.01 to about 1/3, and wherein the carboxylgroups, anhydride groups, or salts thereof are neutralized to an extentof less than about 35% with a fixed base.

According to a sixth aspect of this invention there is provided a methodfor improving the water resistance of a consolidated wood product bytreating the wood components such as, for example, fibers and flakesprior to consolidation with a formaldehyde-free curable aqueouscomposition and curing the composition. Preferably, the curablecomposition contains (a) a polyacid containing at least two carboxylicacid groups, anhydride groups, or the salts thereof; (b) optionally, apolyol containing at least two hydroxyl groups; and (c) aphosphorous-containing accelerator, wherein the ratio of the number ofequivalents of said carboxylic acid groups, anhydride groups, or saltsthereof to the number of equivalents of said hydroxyl groups is fromabout 1/0.01 to about 1/3, and wherein the carboxyl groups, anhydridegroups, or salts thereof are neutralized to an extent of less than about35% with a fixed base.

The following examples are intended to illustrate the method forstrengthening a cellulosic substrate of this invention. They are notintended to limit the invention as other applications of the inventionwill be obvious to those of ordinary skill in the art.

EXAMPLE 1

Preparation of curable aqueous composition.

Preparation of Sample 1.

To 81.6 grams of polyacrylic acid (M.W.=60,000; 25% solids in water) wasadded 5.1 grams glycerol, 3.8 grams of sodium hypophosphite monohydrateand 104.8 grams of methanol. The pH of the mixture was 2.3 and theviscosity was 10 centipoises (measured on a Brookfield LVF viscometer,#4 spindle at 100 rpm). The active ingredients were 15% (activeingredients are all components other than water and methanol).

Sample 1 is a curable aqueous composition of this invention.

EXAMPLE 2.

Preparation of Comparative Sample A

To 93.8 grams of polyacrylic acid (M.W.=60,000; 25% solids in water) wasadded 5.9 grams glycerol, and 95.6 grams of methanol.

Comparative A contains a polyacid and glycerol, an active hydrogencompound, but no phosphorous-containing accelerator.

EXAMPLE 3

Treatment and evaluation of oil- and air-filter paper stock

A 20 mil thick absorbent paper stock suitable for preparing oil or airfilter stock was placed in the aqueous composition of Sample 1 orComparative A; it was then passed through a two-roll Werner Mathis AGpadder to remove excess binder. The roll pressure was adjusted to givethe desired add-on. The treated sheet was dried and cured in a WernerMathis AG oven at 168 C. for a period of time as indicated in Table 3.1.The binder add-on was 28% (dry binder weight based on the weight ofpaper). Comparative sample B is paper stock which is untreated andunheated.

The cured sheet was then cut into 1 inch by 4 inch strips. Strips weretested for dry tensile strength by placing them in the jaws of aThwing-Albert Intelect 500 tensile tester. Samples were pulled apart ata crosshead speed of 2 inches/minute. Wet tensile strength was measuredby soaking a second set of identically prepared cured sheet strips. Thesamples were soaked in 85 C. water for 10 minutes. The samples wereremoved from the water and tested immediately for tensile strength whilestill wet.

The wet tensile strength of a curable aqueous composition-treated filterpaper stock which is a substantial fraction of dry tensile strength of asimilarly treated filter paper stock is taken herein to indicate that acomposition has cured, and that useful performance of the cured aqueouscomposition-treated filter paper stock results.

                  TABLE 3.1                                                       ______________________________________                                        Tensile Testing of Treated Filter paper stock.                                                                  Wet Tensile                                 Sample Cure Time (min.)                                                                           Dry Tensile (lb./in.)                                                                       (lb./in.)                                   ______________________________________                                        1      0            20.8          3.2                                                1            26.5          11.7                                               2            28.4          12.3                                               3            29            15.9                                               5            28.6          15.5                                        Comp. A                                                                              0            23.9          3.4                                                1            23.2          4.1                                                2            2.4           4.8                                                3            20.9          6.5                                                5            17.5          5.0                                         Comp. B                                                                              0            13.2          3.2                                         ______________________________________                                    

Sample 1 of this invention provides levels of wet tensile strengthsuitable for oil- and air-filter stock when cured, while Comparativesample A does not provide useful levels of tensile strength, whethercured or not.

EXAMPLE 4

Preparation of curable aqueous compositions.

Preparation of Samples 2-8 and comparative sample C

To active hydrogen compound, sodium hypophosphite monohydrate (SHP) andwater mixed together was added polyacrylic acid (pAA) (M.W.=10,000; 45%solids in water). Quantities are given in Table 4.1. The degree ofneutralization of the polyacid with a fixed base was <5%. The activeingredients were 10% (active ingredients are all components other thanwater).

                  TABLE 4.1                                                       ______________________________________                                        Compositions of Samples 2-8 and comparative sample C                          Sample g. pAA   g. water g. SHP g. active H compound                          ______________________________________                                        2      85.0     331.7    3.8    0                                             3      65.0     349.7    2.9    10.7  DEA                                     4      52.0     356.6    2.3    17.1  DEA                                     5      38.0     372.8    1.7    24.9  DEA                                     Comp C 70.0     348.4    0      11.5  DEA                                     6      60.0     349.6    5.7    9.85  DEA                                     7      70.0     333.5    3.1    6.7   glycerol                                8      60.0     337.6    2.7    11.5  glycerol                                ______________________________________                                    

Samples 2-8 are curable aqueous compositions of this invention.

EXAMPLE 5

Preparation of curable aqueous compositions at varying degrees ofneutralization.

Preparation of Sample 9 and Comparative Sample D.

To diethanolamine (DEA), sodium hypophosphite monohydrate (SHP) andwater mixed together was added polyacrylic acid (pAA) (M.W.=10,000; 45%solids in water) partially neutralized with sodium hydroxide, a fixedbase. Quantities are given in Table 5.1.

                  TABLE 5.1                                                       ______________________________________                                        Compositions of Sample 9 and Comparative sample D                                    g.                                                                     Sample pAA     g. water g. SHP                                                                              g. DEA % Neutralized                            ______________________________________                                        9      65.0    349.7    2.9   10.7   30                                       Comp. D                                                                              60.0    322.8    2.7   9.9    60                                       ______________________________________                                    

EXAMPLE 6.

Preparation of curable aqueous compositions containing emulsionpolymerized acid-containing compositions.

Preparation of Samples 10-16 and comparative samples E and F.

For samples 10-17 and comparative sample E: To diethanolamine (DEA),sodium hypophosphite monohydrate (SHP), water, and polyacrylic acid(pAA) prepared in the presence of 2% sodium hypophosphite chain transferagent (M.W.=10,000; 45% solids in water) mixed together was added a p(46butyl acrylate/48 ethyl acrylate/4 itaconic acid/2 acrylic acid)emulsion polymer at 45.5% solids content. For sample 17: Todiethanolamine (DEA), sodium hypophosphite monohydrate (SHP), water, andpolyacrylic acid (pAA) prepared in the presence of 2% sodiumhypophosphite chain transfer agent and resulting in phosphinate terminalgroups (M.W.=10,000; 45% solids in water) mixed together was added ap(46 butyl acrylate/46 ethyl acrylate/4 itaconic acid/4 acrylic acid)emulsion polymer at 45.5% solids content. Quantities are given in Table6.1. The degree of neutralization of the polyacid with a fixed base was<5% except for samples 16 and Comp. E, as noted in Table 6.1. The activeingredients were 10% (active ingredients are all components other thanwater).

                  TABLE 6.1                                                       ______________________________________                                        Compositions of Samples 10-17 and Comparative Sample E.                               g.                                                                    Sample  emulsion pol.                                                                            g. pAA  g. water                                                                             a. SHP                                                                              g. DEA                                ______________________________________                                        10      82.0       3.7     340.4  3.7   0                                     11      80.0       3.6     345.6  3.6   0.5                                   12      75.0       3.4     336.9  3.4   2.8                                   13      70.0       3.2     338.3  3.2   5.3                                   14      85.0       3.8     332.8  0     1.6                                   15      70.0       3.2     334.1  6.7   1.3                                   16.sup.1                                                                              78.0       3.5     337.1  3.5   1.5                                   Comp. E.sup.2                                                                         78.0       3.5     337.1  3.5   1.5                                   17      140.0      6.3     552.2  0     3.1                                   ______________________________________                                         .sup.1 30% of acid neutralized with sodium hydroxide, a fixed base            .sup.2 60% of acid neutralized with sodium hydroxide, a fixed base       

EXAMPLE 7

Preparation of curable aqueous compositions containing variouspolyacids.

Preparation of Samples 18-20.

To diethanolamine (DEA), sodium hypophosphite monohydrate (SHP), andwater mixed together was added a polyacid as indicated in Table 7.1.Quantities are given in Table 7.1. The degree of neutralization of thepolyacid with a fixed base was: sample 18--ca. 30%; samples 19-20--<5%.The active ingredients were 10% (active ingredients are all componentsother than water).

                  TABLE 7.1                                                       ______________________________________                                        Compositions of Samples 18-20.                                                Sample                                                                              g. polyacid      g. water g. SHP                                                                              g. DEA                                  ______________________________________                                        18    65.0 p(65 AA/35 MA).sup.1                                                                      349.7    2.9   10.7                                    19    65.0 p(98AA/2 SHP).sup.2                                                                       323.5    0     10.7                                    20    65.0 p(70AA/30HEM5).sup.3                                                                      349.7    2.9   10.7                                    ______________________________________                                         .sup.1 AA = acrylic acid; MA = maleic acid                                    .sup.2 AA = acrylic acid; SHP = sodium hypophosphite present during the       polymerization of the acrylic acid.                                           .sup.3 AA = acrylic acid; HEM5 = CH.sub.2 CH.sub.2 C(O)(OCH.sub.2             CH.sub.2).sub.n OH; n = ca. 5                                            

EXAMPLE 8

Treatment and evaluation of cellulosic nonwovens

Substrates, either 1/2 oz. carded rayon (for sample 17) or WhatmanFilter Paper #4, selected to simulate a cellulosic nonwoven wipe (forsamples 2-16 and 18-20), were saturated on a Birch Brothers' padder. Thesubstrate was disposed between two pieces of fiberglass scrim. The speedcontrol was set at 5 and the pressure at 25 psi. The substrate wasremoved from the scrim after padding and dried and cured in a WernerMathis AG oven at 150-165 C. as noted in Table 6.1 for 3.5 minutes.After removal from the oven, the samples were allowed to cool to roomtemperature and then placed in a temperature (70 F.)/humidity (50% R.H.)controlled room for 24 hours. The binder add-on was 20.3±1.5% (drybinder weight based on the weight of paper).

The cured sheet was then cut into 1 inch by 4 inch strips. Strips weretested for dry tensile strength by placing them in the jaws of aThwing-Albert Intelect 500 tensile tester. Samples were pulled apart ata crosshead speed of 2 inches/minute. Wet tensile strength was measuredby soaking a second set of identically prepared cured sheet strips. Thesamples were soaked in a 0.1% solution of nonionic surfactant (TRITON(R)X-100) in water for 30 minutes. The samples were removed from the waterand tested immediately for tensile strength while still wet. Solventtensile strength was measured by soaking a third set of identicallyprepared cured sheet strips. The samples were soaked in isopropanol(IPA) for 30 minutes. The samples were removed from the isopropanol andtested immediately for tensile strength while still wet.

The wet tensile strength of a curable aqueous composition-treatedsubstrate which is a substantial fraction of the dry tensile strength ofa similarly treated substrate and/or a solvent tensile which iscomparable to the dry tensile strength of a similarly treated substrateis taken herein to indicate that a composition has cured, and thatuseful performance of the cured aqueous composition-treated cellulosicnonwoven results.

                  TABLE 8.1                                                       ______________________________________                                        Tensile (T) Testing of Treated Filter paper stock.                                   Cure C./                        IPA T                                  Sample min.      Dry T (lb./in.)                                                                           Wet T (lb./in.)                                                                         (lb./in.)                              ______________________________________                                        2      165/3.5   6369        1559      5221                                   3      165/3.5   5372        844       5298                                   4      165/3.5   3304        557       3926                                   5      165/3.5   1986        <500      2593                                   Comp. C                                                                              165/3.5   5338        667       5570                                   6      165/3.5   5903        1100      5244                                   7      165/3.5   5246        2158      5007                                   8      165/3.5   4200        2469      4065                                   9      165/3.5   5768        959       5815                                   Comp D.                                                                              165/3.5   5871        961       5979                                   10     150/3.5   5888        2035      2158                                   11     150/3.5   5864        1943      2534                                   12     150/3.5   5724        1939      2618                                   13     150/3.5   5234        1064      2294                                   14     150/3.5   5893        2301      2553                                   15     150/3.5   5453        1493      2535                                   16     150/3.5   5800        1180      2556                                   Comp. E                                                                              150/3.5   5811        <500      2534                                   17     150/3.5   2133        607       N.A.                                   18     165/3.5   2606        <500      3373                                   19     165/3.5   6186        1397      6122                                   20     165/3.5   3390        806       3413                                   ______________________________________                                    

Samples 2-9 relate to curable compositions of this invention whichcontains a polyacid. Samples 2-5 of this invention exhibit useful levelsof wet and solvent tensile strengths for cellulosic nonwoven wipes as afunction of diethanolamine level. Samples 3 and 6 of this inventioncompared to comparative sample C exhibit useful levels of wet tensilestrength for cellulosic nonwoven wipes as a function ofphosphorous-containing accelerator (SHP). Samples 7-8 of this inventionexhibit useful levels of wet and solvent tensile strengths forcellulosic nonwoven wipes at two glycerol levels. Samples 3 and 9 ofthis invention exhibit useful levels of wet and solvent tensilestrengths for cellulosic nonwoven wipes as a function of degree ofneutralization of carboxyl groups.

Samples 10-17 relate to curable compositions of this invention whichcontain an emulsion-polymerized acid-containing copolymer. Samples 10-13of this invention exhibit useful levels of wet and solvent tensilestrengths for cellulosic nonwoven wipes as a function of diethanolaminelevel. Samples 11 and 14-15 of this invention exhibit useful levels ofwet tensile and solvent tensile strength for cellulosic nonwoven wipesat various levels of phosphorous-containing accelerator (SHP);. Samples11 and 16 of this invention exhibit superior wet tensile strengthrelative to Comparative sample E as a function of degree ofneutralization of carboxyl groups with a fixed base.

Sample 17 of this invention used as a binder for a rayon nonwovenexhibits a useful level of dry and wet tensile strength for a cellulosicnonwoven wipe.

Samples 18-20 relate to curable compositions of this invention whichcontain various polyacids and all exhibit useful levels of solventtensile strength for cellulosic nonwoven wipes.

EXAMPLE 9

Preparation of curable aqueous compositions for decorative laminate foilapplications.

Preparation of samples 21-22 and comparative sample F.

To a poly(acrylic acid/ethyl acrylate) copolymer (65 AA/35 EA)(M.W.=20,000; 31.9% solids in water) was added triethanolamine (TEA) orsodium hypophosphite monohydrate (SHP); and water mixed together.Quantities are given in Table 9.1. The degree of neutralization wasapproximated from the measured pH and is given in Table 9.1. The activeingredients were: sample 21-36.4%; sample 22-34.3%; comparative sampleF--31.9% (active ingredients are all components other than water).

Preparation of sample 23.

To triethanolamine (TEA), sodium hypophosphite monohydrate (SHP) andwater mixed together was added poly(acrylic acid) (M.W.=10,000; 45%solids in water). Quantities are given in Table 9.1. The activeingredients were 38% (active ingredients are all components other thanwater).

Preparation of sample 24.

To triethanolamine (TEA) and water mixed together was added apoly(acrylic acid/maleic acid) copolymer (pAA/MA; 55/28) prepared in thepresence of 17% sodium hypophosphite chain transfer agent and resultingin phosphinate groups incorporated in the polymer (M.W.=1500; 55% solidsin water) Quantities are given in Table 9.1. The active ingredients were38% (active ingredients are all components other than water).

Preparation of sample 25.

To 168.6 g. of a poly(acrylic acid/maleic acid) copolymer (pAA/MA;74/20) prepared in the presence of 6% sodium hypophosphite chaintransfer agent (58.5% solids) was added 511.8 g. of an emulsion polymerof p(64 ethyl acrylate/32 methyl methacrylate/4 acrylamide) (45%solids), 172.0 g. water, and 13.5 g. 5N. sodium hydroxide. The polyacidwas 15% neutralized with a fixed base. The active ingredients were 38.2%(active ingredients are all components other than water).

Preparation of comparative sample G.

To form comparative sample G from a separate preparation of sample 24were additionally added 35.7 g. solid sodium hydroxide and 30.0 g. 5Nsodium hydroxide. The active ingredients were 43.4% (active ingredientsare all components other than water).

                  TABLE 9.1                                                       ______________________________________                                        Compositions of Samples 21-24 and comparative samples F-G                     Sample g. polyacid                                                                             g. water g. SHP g. TEA % Neut.                               ______________________________________                                        Comp. F                                                                              500       0        0      0      <5                                    21     500       0        48.0   0      5                                     22     500       0        0      17.9   20                                    23     865.4     387.9    24.4   122.4  30                                    24     391.3     284.1    0      66.7   25                                    Comp. G                                                                              391.3     218.4    0      66.7   50                                    ______________________________________                                    

EXAMPLE 10

Treatment and evaluation of laminating stock

Impregnated, cured papers useful as decorative laminate foils wereprepared by saturating medium weight papers (A=75 grams/square meter;B=82 grams/square meter) with the curable aqueous compositions, samples21-24 and comparative samples F-G. The sheets were placed in the aqueouscomposition bath for 30 seconds and passed through a nip at 12 psi. Thesaturated papers were then cured at 180 C. for 2 minutes in aWerner-Mathis oven using full air flow. Add-on was determined byweighing the samples before saturation and after saturation andcalculating the solids added as a percentage of the initial paper weightand are presented in Tables 10.1 and 10.2 as weight % of the activeingredients deposited based on weight of paper stock.

Delamination Resistance.

The cohesive strength of a single ply of treated paper was measured bycontacting a 1 inch by 1 inch surface of the paper with Scotch MagicTape(TM) for 5 seconds (reported herein as Delam0) or for 18 hours(reported herein as Delam18) at 72 F. and 50% R.H. After the contactperiod the tape was rapidly pulled by hand from the paper in theopposite direction from which the tape was applied. The percentage ofthe area within the I square inch test area which showed no evidence offiber removal was reported.

Flexibility.

Flexibility of the treated paper was determined by conditioning 1.5 cm.by 4.0 cm. specimens at 50% R.H. and 72 F. for 24 hours and rapidlybending the specimens over a mandrel. The average mandrel diameter whichdid not cause cracking of the specimen was reported herein as Flex 50RH.Flexibility at low relative humidity was determined by drying 1.5 cm. by4.0 cm. specimens for 5 minutes at 85 C. in a forced air oven, followedby bending over mandrels, reported herein as Flex LoRH.

Water Absorption (Cobb Test).

A modification of TAPPI Test Method T 441om-84 was used. The procedurewas modified to use 25 ml. of water, reducing the head to 0.25 cm. Thetest period was 60 seconds. One ply of paper was tested at a time. TheAbsorptiveness was calculated as the weight of water absorbed in gramsper square meter and reported herein as Cobb.

Cutability.

The ability of a treated laminate foil to yield a good clean cut underuse conditions was simulated by breaking a treated, cured sheet of stockby hand. A clean break was rated good (G) and a break resulting inprotruding fibers was rated poor (P).

                                      TABLE 10.1                                  __________________________________________________________________________    Results of evaluation of saturated laminating stock A                         Saturant                                                                           Add-on                                                                            Delam0                                                                             Delam18                                                                            Flex 50RH                                                                           Flex LoRH                                                                           Cobb                                                                              Cut.                                       __________________________________________________________________________    Comp. F                                                                            42.3                                                                              52   15   13.5  19.1  50.4                                                                              G                                          21   51.5                                                                              100  99   2.0   15.6  32.8                                                                              G                                          22   46.2                                                                              100  100  1.3   7.9   46.8                                                                              G                                          23   51.3                                                                              100  99   1.8   11.1  68.7                                                                              G                                          24   40.3                                                                              97   95   2.5   9.5   74.9                                                                              G                                          25   43.9                                                                              100  100  0.5   1.8   8.1 G                                          Comp. G                                                                            39.7                                                                              95   55   0.5   4.8   53.5                                                                              P                                          __________________________________________________________________________

                                      TABLE 10.2                                  __________________________________________________________________________    Results of evaluation of saturated laminating stock B                         Saturant                                                                           Add-on                                                                            Delam0                                                                             Delam18                                                                            Flex 50RH                                                                           Flex LoRH                                                                           Cobb                                                                              Cut.                                       __________________________________________________________________________    Comp. F                                                                            29.8                                                                              99   73   4.8   14.3  57.9                                                                              G                                          21   35.6                                                                              100  99   2.3   7.9   44.9                                                                              G                                          22   32.3                                                                              100  100  1.3   4.8   71.0                                                                              G                                          23   36.5                                                                              99   100  2.0   7.2   55.9                                                                              G                                          24   33.2                                                                              100  90   3.1   3.2   64.0                                                                              G                                          25   32.7                                                                              100  90   0.5   2.0   21.5                                                                              G                                          Comp. G                                                                            31.4                                                                              100  40   0.5   9.5   51.7                                                                              P                                          __________________________________________________________________________

Samples 21-23 of this invention exhibit superior delamination resistanceand increased flexibility, and comparable Cobb Water absorption valuesand cutability relative to comparative sample F. Sample 25 exhibitedsuperior delamination resistance, increased flexibility, and superiorCobb Water absorption values and cutability relative to comparativesample F. Sample 24 of this invention exhibits superior delaminationresistance, lessened dependence of flexibility on humidity, and superiorcutability relative to comparative sample G.

EXAMPLE 11

Preparation and Evaluation of Multiple Ply laminates

Preparation of sample 26. To 71.8 g. triethanolamine (TEA) and 169.1 g.water mixed together was added a poly(acrylic acid/maleic acid)copolymer (pAA/MA; 74/20) prepared in the presence of 6% sodiumhypophosphite chain transfer agent and resulting in phosphinate groups(M.W.=3700; 58.5% solids in water). The degree of neutralization of thepolyacid with a fixed base was estimated at 25%, based on the pH of thesample.

A 150 grams/square meter sheet was saturated for 40 seconds in a 47%weight solids bath of sample 24, sample 26, or comparative sample G; thewet saturated sheet was passed through a light nip at 2 psi. The sheetswere dried at 85 C. for 2 minutes to remove excess moisture. Four pliesof the dried impregnated paper were later laminated together by placingthem between platens heated to 180 C. for 15 minutes under a pressure of167 psi. The bonding of the plies of the laminate was evaluated byattempting to pry them apart with a knife edge; results were reported asdelamination resistance.

Gurley stiffness.

Gurley stiffness measures the force required to bend paper underspecific conditions. Blotter stock was prepared with 60% dry add-onofsamples 24, 26, and comparative sample G; the stock was pressed betweenplatens heated to 180 C. for 15 minutes under a pressure of 15 psi. Thepressed blotter stock was equilibrated at 72 F. and 50% R.H. and cutinto strips for testing. The test was conducted according to TAPPI TestMethod T 543 pm-84 using 0.5 inch wide strips and actual lengths of 1.5and 2.5 inches. Gurley stiffness was calculated as mg. of force and ispresented in Table 11.1.

                  TABLE 11.1                                                      ______________________________________                                        Evaluation of Multiple Ply Laminates                                          Sample  Gurley Stiffness (mg.)                                                                        Delamination Resistance                               ______________________________________                                        24      25,100          very good                                             26      37,300          very good                                             Comp. G  6,000          fair-good                                             ______________________________________                                    

Samples 24 and 26 of this invention are suitable for use as impregnantsfor cellulosic stock for laminating applications.

EXAMPLE 12

Preparation and Evaluation of moldable B-stageable Cellulosic Felts

Blotter paper was saturated with sample 23 by immersing the blotterpaper in a 47 weight % solids bath for several minutes. The wetsaturated sheet was passed through two rolls at 2 psi. to squeeze outexcess saturant, and the sheet was dried at 85 C. for 2 minutes toreduce moisture content and to allow handling of the sheet. Dry pick-upwas 43 weight %. Several days later a portion of the sheet was pressedin a stepped mold at 100 pounds pressure and 180 C. for 15 minutes toform and cure the steps. The molded steps were flexed and distorted butreturned to their formed shape, whereas molded but untreated blotterstock could be readily permanently distorted on flexing.

A sheet of the impregnated, uncured blotter prepared as above was cutinto 1.25 inch wide strips which were pressed at 100 psi. and 180 C. for15 minutes. After equilibration of the cured strips at 60% relativehumidity they were transversely bent between two bars 5.5 cm. apartunder a 1 kg. load for 30 minutes at 130 F. The strips had no permanentdeformation.

Two plies of the dried impregnated, uncured blotter paper were pressedtogether at 1000 psi. and 180 C. for 15 minutes to form a laminate. Thelaminate was rigid in appearance and had very strong bonding between theplies. The laminate displayed no adverse effects after immersion for 10minutes in 72 F. water.

Similarly, thick nonwoven cellulose felts were impregnated with 38weight % sample 23 and were dried for 12 minutes at 85 C. to removeexcess moisture. The dried uncured felts were molded into rigid "hats"having sharp angles at 100 pounds pressure and 180 C. for 15 minutes toform and cure the hats. The molded,cured hats had good resistance to 54C. heat and 6.1 kg. of weight applied simultaneously for one hour. Verylittle permanent deformation occurred.

Sample 23 is useful as a B-stageable impregnant suitable for molding andlaminating cellulosic stock into high strength structures.

EXAMPLE 13

Evaluation of durable press performance of cotton fabric treated withcurable aqueous composition

A desized, scoured, and bleached 100% cotton print cloth (Style 400 fromTest Fabrics, Inc., Middlesex, N.J.) was used. The material was 45inches wide and weighed 3.1 ounces per square yard. Finishing solutionssamples 27-30 and comparative sample H were prepared the day before theywere used in padding the samples. A 1000 g. finishing solution wasprepared at 7.5 weight percent solids of the treatment polyacid,optional active hydrogen compound, and phosphorous-containingaccelerator components in deionized water. Other additives were added asdisclosed but in addition to the 7.5 weight percent value. The pH wasadjusted to 3.0 with NaOH or HCl as required.

The fabric was cut into 16 inch(warp) by 13 inch(filling) sheets andconditioned in the laboratory prior to padding. Three sheets of finishedcloth were prepared for each sample. The sheets were weighed and thenpadded using a double dip-nip sequence on a Werner-Mathis padder. Theroll pressure was set at 6.0 bars, and roll speed was 6.0 meters persecond. The samples were weighed immediately and wet pick-up wascalculated. These conditions provided a wet pick-up of approximately 67%on weight of fabric and a calculated dry add-on of approximately 4.5% onweight of fabric. The wet sheets were suspended and pinned under lighttension in the warp direction on a frame. The samples were dried/curedfor 3.5 minutes at 180 C. in one operation using a Werner-Mathis oven.The oven was set for full air flow and equal top to bottom airimpingement on the sample. All samples were conditioned in the specifiedenvironment prior to testing.

Sample 27 was a p(55% acrylic acid/28% maleic acid) copolymer preparedin the presence of 17 weight% sodium hypophosphite (M.W.=2000). Thedegree of neutralization of the polyacid with a fixed base was 20%.

Sample 28 was a p(39.3% acrylic acid/25.7 % maleic acid) copolymerprepared in the presence of 35 weight % sodium hypophosphite (M.W.=960).The degree of neutralization of the polyacid with a fixed base was 20%.

Comparative sample H was a p(20% acrylic acid/80% maleic acid) copolymer(M.W.=2210). The degree of neutralization of the polyacid with a fixedbase was 20%.

Sample 29 was sample 28 with added 25 weight % sodium hypophosphite onweight of polymer solids. Total solids of the sample was 7.5%. Thedegree of neutralization of the polyacid with a fixed base was 20%.

Sample 30 was 1,2,3,4-butanetetracarboxylic acid to which was added85.65 weight % sodium hypophosphite on weight of the polyacid. Thedegree of neutralization of the polyacid with a fixed base was 10%.

Sample 31 was formed from 111.5 g. polymer p(70.6% maleic acid) preparedin the presence of 29.4 weight % sodium hypophosphite (M.W.=470) (67.3%solids) and 888.5 g. water. The degree of neutralization of the polyacidwith a fixed base was 20%.

Sample 32 was formed from 111.5 g. polymer p(70.6% maleic acid) preparedin the presence of 29.4 weight % sodium hypophosphite (M.W.=470) (67.3%solids), 6.1 g. triethanolamine, and 882.4 g. water. The degree ofneutralization of the polyacid with a fixed base was 10%.

Comparative sample I was untreated cloth.

Wrinkle Recovery was determined using AATCC Test method 66-1990. Thetest measures the recovery, in degrees, of a creased and compressedspecimen which is suspended in the test instrument for a controlledrecovery period. Three test specimens (15 mm. by 40 mm.) were cut in thewarp and filling directions from each of two replicate sheets. Thespecimens were conditioned overnight at 65% R.H. and 70 F. prior totesting. The average recovery angle was calculated for each direction.The combine recovery angle was calculated by adding the average warp andfilling angles and is reported herein as wrinkle recovery.

Handle was measured using a Thwing-Albert Handle-O-Meter, Model 211-5.Three 4 inch by 4 inch specimens were cut from each of two replicatesheets and were conditioned at 65% R.H. and 70 F. prior to testing. TheH-O-M slot width was set at 5 mm. Measurements were taken in each offour positions per specimen as required by the instrument manufacturer'stest manual, and the four measurements were summed to give the handlefor a single specimen. The average handle for the 6 specimens wascalculated and reported herein as Handle-O-Meter.

Tensile strength was determined according to ASTM Test Method D1682-64.Tear strength was determined according to ASTM Test Method D1424-83. %Retained values reported herein refer to the % of the untreated, uncuredvalue retained after treatment and curing.

Yellowness was determined using a Hunter ColorQuest instrument. Theinstrument was calibrated and operated in the reflectance mode with thespecular light excluded. Illuminant C was used. The observer angle was10 degrees. The color of undyed, finished cotton print cloth wasmeasured on six 4 inch by 4 inch specimens which were folded over twice(4 thicknesses of cloth per specimen) to provide 24 total thicknesses ofbacking when making each measurement. The average b* value was recordedfor the test and untreated control samples. Delta b*, expressed as thedifference of the control value minus the test sample value for the b*parameter, was calculated for each test sample. Higher values of Deltab* indicate yellower samples.

                  TABLE 13.1                                                      ______________________________________                                        Evaluation of finished cotton fabric                                                           Handle-  %             Yellow-                                      Wrinkle   O-       Tensile                                                                              % Tear ness                                  Sample Recovery  Meter    Retention                                                                            Retention                                                                            Delta b*                              ______________________________________                                        27     224       66       72     74     .12                                   28     217       59       78     78     .25                                   Comp. H                                                                              209       64       63     64     .94                                   29     211       65       73     74     1.27                                  30     251       57       60     64     1.14                                  Comp. I                                                                              177       58       100    100    0                                     31     211       67       73     na     .72                                   32     216       70       70     na     .97                                   ______________________________________                                    

Samples 27-32 of this invention exhibit superior wrinkle recoveryrelative to untreated fabric, comparative sample I. Addition polymerpolyacids, samples 27-29, 31, and 32 of this invention, exhibit superiortear and tensile retention compared with low molecular weightnon-polymeric polyacids as exhibited by sample 30. Sample 29 of thisinvention incorporating phosphorous-containing accelerator exhibitssuperior tensile and tear retention relative to the same compositionwithout phosphorous-containing accelerator (Comparative H). Samples 27and 28 of this invention wherein the polyacid component incorporates thephosphorous-containing accelerator exhibit superior (lower) yellowingwhile maintaing a useful level of other treated, cured fabricproperties.

EXAMPLE 14

Evaluation of Consolidated Wood Product Treated with Curable AqueousComposition

Comparative sample J was polyacrylic acid (M.W.=10,000). The degree ofneutralization of the acid with a fixed base was approximately 25%(pH=4).

Sample 33 was 100 g. by dry weight polyacrylic acid (M.W.=10,000) towhich 10 g. triethanolamine and 5 g. sodium hyposphosphite was added.The degree of neutralization of the acid with a fixed base wasapproximately 25% (pH=4).

A 20% solids sample of sample 33 or comparative sample J was sprayedinto wood chips tumbling in an open-ended drum. The wood chips varied insize but a chip of 1/4 inch by 1/16 inch by 1/64 inch was typical. After5 minutes of tumbling the chips were placed in a 6 inch by 6 inchforming box and compressed at 100 psi at ambient temperature for 1minute to form a mat. The mat was then pressed to form a consolidatedwood product, a flakeboard, under conditions of 350 F. and 278 psi. for3 minutes resulting in a board density of 0.7 grams/cc. The board wasthen cut into 2 inch by 2 inch test specimens and immersed in boilingwater for 30 minutes. The board was removed and its thickness measuredwith calipers. The % swell as reported herein was calculated relative tothe treated, cured pressed board which had not been subjected to theboiling water; a rating of "fail" indicated that the board disintegratedat least in part. The modulus of rupture (MOR) of the board in psi. wasalso determined. Results are presented in Table 14.1.

                  TABLE 14.1                                                      ______________________________________                                        Evaluation of consolidated flake boards                                       Sample        % Swell  MOR (psi.)                                             ______________________________________                                        Comp. J       Fail     938                                                    33            70       935                                                    ______________________________________                                    

Sample 33 of this invention was an effective binder for a consolidatedwood product.

What is claimed is:
 1. A method for increasing the delaminationresistance of laminating stock or a laminate comprising multiple pliesof said laminating stock comprising contacting said laminating stockwith a formaldehyde-free curable aqueous composition comprising (a) apolyacid containing at least two carboxylic acid groups, anhydridegroups, or the salts thereof; and (b) a phosphorous-containingaccelerator, wherein said carboxyl groups, anhydride groups, or saltsthereof are neutralized to an extent of less than about 35% with a fixedbase; and heating said composition.
 2. The method of claim 1 whereinsaid curable aqueous composition further comprises at least one activehydrogen compound, said active hydrogen compound comprising at least twoactive hydrogen groups selected from the group consisting of hydroxyl,primary amino, secondary amino, and mixtures thereof; wherein the ratioof the number of equivalents of said carboxylic acid groups, anhydridegroups, or salts thereof to the number of equivalents of said activehydrogen groups is from about 1/0.01 to about 1/3.
 3. The method ofclaim 1 wherein said polyacid comprises a copolymer prepared by emulsionpolymerization of at least two ethylenically-unsaturated monomers andcontains at least two carboxylic acid groups, anhydride groups, or thesalts thereof; wherein said copolymer has a Tg between about 60 C. andabout -50 C.
 4. The method of claim 1 wherein said polyacid is anaddition polymer formed from at least one ethylenically-unsaturatedmonomer.
 5. A method for improving the water resistance of aconsolidated wood product comprising contacting said wood productcomponents, prior to consolidation, with a formaldehyde-free curableaqueous composition comprising (a) a polyacid containing at least twocarboxylic acid groups, anhydride groups, or the salts thereof; and (b)a phosphorous-containing accelerator, wherein said carboxyl groups,anhydride groups, or salts thereof are neutralized to an extent of lessthan about 35% with a fixed base; and heating said composition.
 6. Themethod of claim 5 wherein said curable aqueous composition furthercomprises at least one active hydrogen compound, said active hydrogencompound comprising at least two active hydrogen groups selected fromthe group consisting of hydroxyl, primary amino, secondary amino, andmixtures thereof; wherein the ratio of the number of equivalents of saidcarboxylic acid groups, anhydride groups, or salts thereof to the numberof equivalents of said active hydrogen groups is from about 1/0.01 toabout 1/3.
 7. The method of claim 5 wherein said polyacid is an additionpolymer formed from at least one ethylenically-unsaturated monomer.